Drawing instrument



April 27, 1954 E, E, wE s sg 2,676,511

DRAWING INSTRUMENT Filed Aug. 22. 1950 f TRAN PAREM J5 A97 INVENTOR.

E452 we'ksas'e Patented Apr. 27, 1954 UNITED STATES PATENT OFFICE DRAWING" INSTRUMENT Ernst E. Weisse, Dusseldorf, Germany npplicationnugustzz, 1950, Serial No. 189,073

6- Claims. 1

This invention relates to" a drawing instrument and more particularly it has reference: to a spe-- cial kind of rulers and their use in drawing pax allels, normals and. angles. It. was usual here-- tofore to guide rulers parallel on straightedges, or by parallelogram type of: linkage systems or similar means. However; such mechanical guides are attended by certain disadvantages which are overcome by the present invention. Drawing: instruments equipped with parallelogram type of linkage systems become rather big, unhandyand expensive. Mechanical edges which might serve: for guiding a T'-square,. very often are not straight or not on hand as; for example, when drawing: without drawing board, or when" layingv out a workpiece on atable or bench.

In contradistinction to methods of guiding a ruler mechanically, the invention is based on the idea to provide a ruler or'straightedge with optical means so as to permit its" accurate and "con-- venicnt alignment with a drawn line or with an edge of the drawing paper; Such an optically equipped ruler can be conveniently positioned to be parallel,- perpendicular or at a certain angle to a line.

Suitable arrangement and construction" of the: optical means for aligning the ruler renders it. possible to draw infinitely long lines without raising the pencil from the paper.

By employing the teaching of the: present invention it is possible to create a drawing device which has the following advantages: small in size and light in. weight so that it may be carried conveniently in. a brief case, applicable universally and. working with sufficien't accuracy not withstanding its small size, and inexpensive to manufacture.

These and other objects; advantages and applications of the invention will more fully appear from the following description made in connection with the accompanying drawings in. which. one embodiment of the invention isillustrated diagrammatically by way of. example.

In sai'd'drawingsz Fig; 1 is a perspective of a prism lying on the surface of the drawing paper,

Fig. 2 is a top plan view of the drawing instrument'provided by the invention,

Fig. 3 is a sectional view taken at line 3'-3 of Fig. 2",

Fig. 4' is a longitudinal sectional view taken at lined-4' of Fig. 2, and

Fig. 5 is a perspective View showing the-con nectihg means of two rulers articulated withone another and a device for indicating; the angular position ofthe-rulereas to each other;

' gree's.

If, as shown in Fig, 1, a transparent prism I having the cross-sectional form. of an isosceles right'angled triangle is placed with its face 2,. bounded. by the hypotenuse, upon the surface oi the drawing paper, then all lines running oblique to the apex edge 3 of the prism l (e g. the lines 4 and 5) appear to be broken on said apex edge 3. Those parts of the particular line which run perpendicular to the apex edge 3 (i. e. line 6') meet exactly at this apex edge 3. This effect can: be observed fromany direction without it bein ossible that parallax errors occur. The accurateperpendicular alignment of such a prism. with a drawn line or with an edge of the drawing paper is therefore quite easy to accomplish The sensitivity of the alignment can be increased by placing the prism not directly upon the surface of the paper but leaving: a distance between the surface of the paper and the face 2 of the prism. The" greater this distancethe greater the sensitivity; By using, by way of example, a ruler, having the cross-sectional form illustrated Fig; 3, it is possible to obtain a very high sensitivity of alignment rendering it possible. to discern: angular deviations of several: do An observer looking down upon such a prism-from above- F'ig. 3) will then see through the face 1 of the prism, due to the refractive efiect of the prism, a portion m- -p of a line drawn perpendicular to the apex edge 9 on the surface zc of. the" paper, while, when looking through. the face a an. observer will then see the line portion Accordingly; two spaced apart points 11- andp" oi. a straight line: will then be seen directly side: by side on the apex edge 5'. If the line portion is not exactly perpendicular to the apex edge 9 then the a parent break in the continui'ty of the line will be seen on the apex edge 9,.as clearly shownin Fig. l. The cross-sectional term of theruler is so formed that the face l0,- bounded by the hypotenuse of the prism, is situ-' ated at a. substantialv distance above the: suriace' za or the paper, yet permitting; the free passage therethrough of rays (indicated by dotted lines)" down to the" surface Z'e of thepaper. The oblique side faces H and I2 resulting therefrom are formed as cylinder" lenses and they concentrate the light falling upon the ruler for the purpose of better illumination of the surface Ze of the paper: The surfaces of the ruler adjoining the fiducialedges f 3, H are as usual provided with scale'means for measuring.

The drawing instrument illustrated in Fig. 2 consists of. two iulers l5, 16 having the. cross sectional form: previously illustrated and de-'- dfibd iii connection Willi-1mg; 3. In

the ruler I5 is provided with another prism l1 whose apex edge [8 is arranged so as to be perpendicular to the fiducial edges of the ruler l5. Besides the longitudinal prism I9 the ruler I6 is provided with two transverse prisms 20, 2| projecting beyond the fiducial edge 22. For that reason it is possible to draw a line on the fiducial edge 22, then move the ruler along the point of the pencil and align it by means of the prism 20 or 2| with said previously drawn line and then continue to draw the line. Thus it is possible to draw infinitely long lines without raising the pencil from the paper, although the fiducial edge 22 is relatively short.

Integral with the ruler I6 is a pivot joint collar 23 provided with a semi-circular scale 24 for indicating the angular positions. A small line 26 serving as fiducial line is arranged on the collar 23 exactly opposite to the center of the scale 24.

' The ruler is with its ear 23 is articulated by means of a post 2! to the ruler 15, the post 2'! being an integral part of the ruler IS. The rulers l5 and it can be held in any angular position in relation to each other by means of a screw 28 and a locking device 29. The post Z'Iis provided with a frame-like member 36 mounted above'the surface of collar 23 and having a "transparent mirror 3|. An observer looking down upon the mirror 3|, as shown in Fig. 5, will see, since it is semi-pervious, the scale .24, yet at the same time also the reflection 32 of the fiducial line 26 moving over the whole scale 24; and so the reflection always moves by an angle which is twice as large as the particualr angle by which the ruler [5 with the mirror 3| has been swung. The scale 24 is therefore so constructed that the quadrant of the circle is graduated in forty-five angular degrees. Thus, by means of the reflected indicia it is possible to set the angular position of the'two rulers in relation to each other essentially with double sensitivity.

The rulers l5 and IS with their integral articulated joints (ear 23 and collar 21 respectively) and any desirable graduations, indicia and lettering may be cheaply manufactured from clear thermoplastic materials or such likeby means of the injection die-casting process or the like.

What is'claimed is:

1. As a new article of manufacture, a ruler comprising an elongated transparent basemember having a planar undersurface and a straight fiducial edge extending lengthwise along one side of said base member, and an elongated transparent isosceles triangular prism fixedly mounted upon said base member a substantial distance above said planar undersurface, said prism being arranged with the apex edge thereof uppermost and parallel to said straight fiducial edge of said base member and with the prism face remote from said apex edge parallelto said planar undersurface whereby spaced points on a straight line viewed through said prism appear immedi= ately adjacent each other and in' alignment with said straight line when the apex edge of said prism is perpendicular to said straight line.

2. As a new article of manufacture, a ruler comprising an elongated transparent base member having a planar undersurface and a straight fiducial edge extending lengthwise along one side of said base member, and an elongated transparent isosceles triangular prism. fixedly mounted upon said base member a substantial distance above said planar undersurface, said prism being arranged with the apex edgethereof uppermost and perpendicular to said straight fiducialedge of said base member and extending over and beyond said fiducial edge and with the prism face remote from said apex edge parallel to said planar undersurface whereby spaced points on a straight line forming substantially an extension of said fiducial edge viewed through said prism appear immediately adjacent each other and in alignment with said straight line when the apex edge of said prism is perpendicular to said straight line.

3. As a new article of manufacture, a ruler comprising an elongated transparent base member having substantially an inverted U crosssection and a straight fiducial edge extending throughout the length thereof at the extremity of at least one leg thereof, and an elongated transparent isosceles triangular prism fixedly mounted upon said base member at the juncture of the two legs thereof, said prism being arranged with the apex edge thereof uppermost and parallel to said straight fiducial edge of said base member and with the prism face remote from said apex edge parallel to the plane defined by the extremitiesof the two legs of said U-sectioned base member whereby spaced points on a straight line viewed through said prism appear immediately'adjacent each otherand in alignment with said straight line when the apex edge of said prism is perpendicular to said straight line.

4; In a drawing instrument, the combination of two rulers pivotally joined at one end thereof, one of said rulers comprising an elongated transparent base member having a planar undersurface and a straight fiducial edge extending lengthwise along one side of said base member, and an elongated transparent isosceles triangular prism fixedly mounted upon said base member a substantial'distance above said planar undersurface, said prism being arranged with the apex edge thereof uppermost and parallel to said straight fiducial edge of said base member and with the prism face remote from said apex edge parallel to said planar undersurface whereby spaced points on a straight line viewed through said prism appear immediately adjacent each other and in alignment with said straight line when the apex edge of said prism is perpendicular to said straight line, the second of said rulers having a straight edge extending lengthwise along one side thereof.

5. In a drawing instrument, in combination, a first and a second ruler each comprising an elon-. gated base member having a planar undersurface and a straight fiducial edge extending lengthwise along one side of saidbase member, said first ruler having a pivot post at one end perpendicular to said planar undersurface, said second ruler having a circular collar surrounding said pivot post and forming therewith a pivot joint for said first and second rulers, semi-circular indicia upon said collar and a fiducial mark upon said collar opposite said indicia, and an erect transparent mirror mounted upon said post at the axis thereof through which said indicia may be viewed and the position of the image of said fiducial mark with reference to said indicia may be noted and the relative angular relationship of the two rulers thus determined, at least one of said rulers having an elongated transparent isosceles triangular prism mounted upon the base member of said ruler a substantial distance above the planar undersurface thereof, said prism being arranged with the apex edge thereof uppermost and parallel to the straightfiducial edge of face remote from the apex edge parallel to the planar undersurface of the base member of said ruler whereby spaced points on a straight line viewed through said prism appear immediately adjacent each other and in alignment with said straight line when the apex edge of said prism is perpendicular to said straight line.

6. As a new article of manufacture, a ruler comprising an elongated transparent base member having a planar undersurface and a straight fiducial edge extending lengthwise along one side of said base member, and a. first and a second elongated transparent isosceles triangular prism both fixedly mounted upon said base member a substantial distance above said planar undersurface, said first prism being arranged with the apex edge thereof uppermost and parallel to said straight fiducial edge of said base member, said second prism being arranged with the apex edge thereof uppermost and perpendicular to said straight fiducial edge of said base member and extending over and beyond said fiducial edge, both of said prisms being arranged with the prism faces thereof remote from the apex edges thereof parallel to said planar undersurface whereby spaced points on a straight line viewed through either of said prisms appear immediately adjacent each other and in alignment with said straight line when the apex edge of the prism through which said straight line is viewed is perpendicular to said straight line.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 781,117 Willits Jan. 31, 1905 830,769 Chandler Sept. 11, 1906 1,550,755 Steinle Aug. 25, 1925 1,640,425 Percival Aug. 30, 1927 1,907,873 Richards et al May 9, 1933 2,023,539 Packard Dec. 10, 1935 2,028,063 Green Jan. 14, 1935 2,377,937 Whitmore June 12, 1945 2,445,792 Lunney July 27, 1948 2,531,248 Belch Nov. 21, 1950 FOREIGN PATENTS Number Country Date 27,429 Great Britain Dec. 15, 1903 545,262

Great Britain May 18., 1942 

